1. Rack it to secondary before tucking it away. Lambic is really the only fermentation profile that benefits from autolyzed and trub.
When you add oak chips it depends on your preference for oak flavors in the style. I really like the vanilla character in mine, so I add cubes when I rack to secondary. I use 0.25 oz or so since it will still sit on them a long time, but so I dont have to pull a lot of samples to taste for oak when I know the beer isn't nearly ready. A little goes a long way for a Flanders, and it isn't necessarily traditional to have a lot of oak character, so judges can ding you for it.
I always err on the side of keeping as much O2 out as I can through conditioning. Acetic WILL develop over time, so don't worry about an oak stopper. Use a rubber stopper w/ filled airlock since you will get some gas evolution over time.
If the beer is ready and it doesnt have enough acetic for your liking, you can doctor it with actual vinegar (or older flanders as you brew more).
If its for a competition, judges are many times over-sensitive to acetic. I doubt a judge will comment "boy, this could SURE use some more vinegar!"
Limit samples. I don't even touch it for 6 months.